1. Field of the Invention
The present invention relates to a tilting pad bearing.
2. Description of the Related Art
The fluid bearing (liquid bearing) is a shaft bearing that supports the load of a rotary shaft via a thin fluid film. The fluid bearings have higher load bearing performance compared to rolling bearings and also excel in vibration damping properties. Therefore, the fluid bearings are widely employed for industrial large-sized rotary machines (steam turbines, generators, etc.) required to have high reliability. As a type of the fluid bearing, there exists a tilting pad bearing excelling in oscillation stability.
The tilting pad bearing comprises a bearing housing and a plurality of pads which are arranged to be pivotable (tiltable) with respect to the bearing housing. Lubricating oil is supplied to the gaps between the rotary shaft and the pads to form oil films, and the rotary shaft is supported by the pressure of the oil films. Since the tilting angle of each pad changes according to the pressure distribution of the oil film, unstable oscillation such as the so-called “oil whip” can be suppressed.
A direct oil supply method is well known as one of the oil supply methods for the tilting pad bearing. In the standard type of direct oil supply method, the lubricating oil is supplied to the gap between the rotary shaft and the sliding surface of each pad from an oil supply hole that is open on a front edge part of the sliding surface of the pad, or the lubricating oil is supplied from each oil supply nozzle arranged between adjacent pads to the gap between the rotary shaft and the sliding surface of the pad situated downstream of the oil supply nozzle. With these methods directly supplying low-temperature lubricating oil to the gaps between the rotary shaft and the sliding surfaces of the pads, the temperature rise of the sliding surfaces of the pads can be suppressed. Consequently, the amount of oil supply can be reduced.
There is another known method (see JP-2009-063015-A, for example) in which the lubricating oil is supplied via an oil channel (cooling channel) formed inside each pad to the gap between the rotary shaft and the sliding surface of the adjacent pad. In this method, low-temperature lubricating oil is first distributed to the oil channel of each pad and then supplied to the gap between the rotary shaft and the sliding surface of the next pad on the downstream side. Therefore, the temperature rise of the sliding surfaces of the pads can be suppressed further compared to the standard type of direct oil supply method. Consequently, the amount of oil supply can be reduced further.